The giant slug Limax maximus expresses a circadian rhythm in locomotor activity with a period of about 24 h. The rhythm is temperature compensated with a Q10 of about 1.00. We propose to study variations in spontaneous neural activity of Limax brains kept in organ culture for a week or more under 24 h temperature cycles. We will attempt to compare the induced neural rhythm with the locomotor rhythm of the intact animal when entrained to similar temperature cycles. In addition, we plan to look for evidence of endogenous rhythmicity in cultured brains following 3 days of an in vitro temperature cycle to synchronize neural activity. Finally, experiments will be conducted using brains from both acclimated and non-acclimated animals in which we will attempt to determine Q10 values for spontaneous neural activity in an effort to understand the physiological basis for temperature compensation of the behavioral rhythm.